Journalist Isa Balado of Cuatro channel was reporting on a robbery in Madrid for channel Cuatro on Tuesday, September 12, when a man approached her and put his hand on her behind before asking her which television channel she worked for.
Balado was interrupted by the news programme's host, Nacho Abad, who was speaking to her from the TV studio.
"Isa, forgive me for interrupting you... but did he just touch your butt?" he asked.
"Yes," the reporter replied.
Sounding angered, Abad insisted she put the "idiot" on camera.
Balado confronted the man in the street and told him that she had been trying to do her job.
"As much as you want to ask what channel we are from, do you really have to touch my ass? I'm doing a live show and I'm working," she said.
The man immediately denied touching her bottom - and as he walked away, rubbing her hair.
He continued to linger in the street and approached her once more, while she was still live on air, and said he had heard her accusations and she should "tell the truth".
Balado asked for the live broadcast to be cut because she did not want to give the man any more attention.
Police said in a post on X, formerly known as Twitter, that a man had been arrested for sexually assaulting a reporter live on air.
Mediaset Espana, owner of the news channel, issued a statement expressing its full support for Balado.
The company said she had experienced an "absolutely intolerable situation" and added it "categorically rejects any type of harassment or aggression".